ASM case reports · 2025
Bacteremia due to a rare opportunistic pathogen, Kluyvera intermedia, with atypical antimicrobial susceptibility in the absence of β-lactamases.
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Luong Tevan, Weiland Anatasia, Hsieh Lanny, Khan Ayesha
Аннотация
BACKGROUND: Kluyvera are gastrointestinal commensals and emerging opportunistic pathogens. Kluyvera are considered intrinsically resistant to ampicillin and early generation cephalosporins due to chromosomal β-lactamase encoding bla KLU genes, which are the proposed ancestors of modern CTX-M enzymes.
CASE SUMMARY: Here, we present a case of bacteremia and septic shock in a 61-year-old patient with uncontrolled type 2 diabetes caused by the rare species, Kluyvera intermedia. It was misidentified as "Enterobacter (non-cloacae complex)" by the ePlex blood culture molecular identification panel. The K. intermedia displayed atypical susceptibility to all β-lactams that diverge from previous clinical case reports on Kluyvera. The patient was successfully treated with piperacillin-tazobactam and surgical source control. Only one clinical case of K. intermedia infection has been reported before. We identified three other cases at our institution from 2023 and 2024, including two severe infections. Analysis of 162 publicly available Kluyvera genomes on NCBI revealed that chromosomal bla KLU genes are not uniformly present in all Kluyvera species. Strikingly, chromosomal bla KLU genes are present in 0% of K. intermedia genomes; 100% of Kluyvera ascorbata, Kluyvera cryocrescens, and Kluyvera sichuanensis genomes; and 50% of other Kluyvera species genomes. There is also extensive diversity in the prevalence of plasmid-mediated extended-spectrum β-lactamases and carbapenemases across Kluyvera species.
CONCLUSION: This case highlights clinically relevant, species-specific genomic variation in Kluyvera that impacts antimicrobial susceptibility and treatment. K. intermedia has a distinct genomic landscape of antimicrobial resistance than other Kluyvera species, suggesting that the origin of CTX-M enzymes may still be unknown. This case underscores the importance of utilizing culture-based identification and phenotypic susceptibility testing to guide the treatment of Kluyvera infections.
CASE SUMMARY: Here, we present a case of bacteremia and septic shock in a 61-year-old patient with uncontrolled type 2 diabetes caused by the rare species, Kluyvera intermedia. It was misidentified as "Enterobacter (non-cloacae complex)" by the ePlex blood culture molecular identification panel. The K. intermedia displayed atypical susceptibility to all β-lactams that diverge from previous clinical case reports on Kluyvera. The patient was successfully treated with piperacillin-tazobactam and surgical source control. Only one clinical case of K. intermedia infection has been reported before. We identified three other cases at our institution from 2023 and 2024, including two severe infections. Analysis of 162 publicly available Kluyvera genomes on NCBI revealed that chromosomal bla KLU genes are not uniformly present in all Kluyvera species. Strikingly, chromosomal bla KLU genes are present in 0% of K. intermedia genomes; 100% of Kluyvera ascorbata, Kluyvera cryocrescens, and Kluyvera sichuanensis genomes; and 50% of other Kluyvera species genomes. There is also extensive diversity in the prevalence of plasmid-mediated extended-spectrum β-lactamases and carbapenemases across Kluyvera species.
CONCLUSION: This case highlights clinically relevant, species-specific genomic variation in Kluyvera that impacts antimicrobial susceptibility and treatment. K. intermedia has a distinct genomic landscape of antimicrobial resistance than other Kluyvera species, suggesting that the origin of CTX-M enzymes may still be unknown. This case underscores the importance of utilizing culture-based identification and phenotypic susceptibility testing to guide the treatment of Kluyvera infections.